Hagfish are widely considered the most disgusting animals in the ocean, if not on earth. The eel-shaped creatures use four pairs of thin sensory tentacles surrounding their mouths to find food—including carcasses of much larger animals. Once they find their meal, they bury into it face-first to bore a tunnel deep into its flesh.

Despite the fact that they seem repulsive, they are undoubtedly unique—and just because animals are disgusting to human sensibilities doesn’t mean they don’t deserve our attention and protection. That is the message behind Hagfish Day, which occurs every year on the third Wednesday of October: that we can find beauty in the ugly and protect all ocean animals. Here are 14 fun facts about the unusual group of animals:

5. Although they are jawless, hagfish have two rows of tooth-like structures made of keratin that they use to burrow deep into carcasses. They can also bite off chunks of food. While eating carrion or live prey, they tie their tails into knots to generate torque and increase the force of their bites.

7. No one is sure whether hagfish belong to their own group of animals, filling the gap between invertebrates and vertebrates, or if they are more closely related to vertebrates.

8. The only known fossil hagfish, from 300 million years ago, looks very much like a modern hagfish, leading some scientists to speculate that it has changed little since then. “It’s an indication, not that they’ve stalemated and are not evolving, but that they have arrived at a body plan that is still very successful today,” says Tom Munroe, a fish zoologist at the Smithsonian National Museum of Natural History.

13. Not only are hagfishes jawless, but they are also boneless. They have a skull made of cartilage, but no vertebrae.

14. Hagfish are threatened from both intentional fishing and unintentional bycatch. Hagfish weren’t always fished, but because several more preferable fish species are overfished and hard to catch, fishermen have moved down to catching hagfish.

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